1. Field of the Invention
The present invention relates to an improved catheter apparatus for percutaneous coronary intervention (PCI), and more particularly to a catheter apparatus for PCI whereby a balloon catheter can be moved more accurately to place a balloon formed at the distal end of the balloon catheter and a stent mounted on the balloon in a position of a human coronary artery having a cardiovascular disease such as a stenotic lesion.
2. Description of the Related Art
Coronary arteries of a human blood circulation system are tubes that supply the heart with oxygen, blood and nutritive substances. The left and right coronary arteries branching off from the ascending aorta spread over the surface of the heart as if to enclose the heart.
PCI has recently become a commonly performed technique for treating cardiovascular diseases such as stenotic lesions and abrupt vessel closure of coronary arteries. A stenotic lesion is an abnormal narrowing of an artery usually due to atherosclerosis.
More than 15,000 PCI procedures are performed yearly in the Republic of Korea, and it has been estimated that more than 100,000 procedures are performed annually in Japan and more than 1,000,000 procedures are performed annually in the U.S.
In PCI treatment, a balloon catheter is inserted through a femoral or brachial artery of the patient to introduce the balloon formed at the distal end of the balloon catheter to the obstructive lesion of the coronary artery. Next, inflation of the balloon with a fluid (i.e. contrast media) causes the obstructive lesion of the coronary artery to become more open.
PCI treatment also involves the introduction into the coronary artery of a stent, which generally has a metal tubular meshwork structure and is mounted on the inflatable balloon at the distal end of the balloon catheter, through the femoral artery or the brachial artery, and the introduction of the balloon and the stent to the stenotic lesion of the coronary artery. Subsequently, the balloon is inflated with a fluid which expands the stent causing the stent to undergo a plastic deformation, thereby installing the stent within the walls of the coronary artery. After the balloon is deflated and pulled back out of the lesion, the stent is left behind in place so as to keep the blockage open by continuously supporting the interior walls of the artery with radial force.
FIG. 1B is an illustration of the conventional catheter apparatus 1 for PCI including a balloon catheter, a guiding catheter, etc., in which all parts of the apparatus are assembled. FIG. 1C is an illustration of the catheter apparatus 1 shown in FIG. 1B, in which certain pieces are disassembled from the whole apparatus. FIG. 1D is an illustration of a stent 8 mounted on the inflatable balloon 5a at the distal end of the balloon catheter 5 shown in FIGS. 1B and 1C.
A conventional catheter apparatus 1 for PCI includes a Y-connector 2, an introducer set 3, a guiding catheter 4, a balloon catheter 5, a guidewire 6, a clamp 7 and a stent 8. Among these components, the Y-connector has a main tube 2a and a side tube 2b. The guiding catheter 4 which is introduced into the introducer set 3 is coupled with the main tube 2a of the Y-connector 2. The guidewire 6 and the balloon catheter 5 pass through the main tube 2a of the Y-connector 2, and the side tube 2b is coupled with a pipe of a manifold 9.
The manifold 9 has a plurality of pipes that are coupled with a pressure sensing device 9a, a physiological saline solution bottle 9c and a contrast media injection syringe 9d, respectively. In addition, the manifold 9 has a plurality of valves for controlling the flows of several fluids, installed inside the pipes of the manifold 9, respectively.
As much as is needed of the contrast media contained in the contrast media bottle 9c may be injected into the patent's artery by way of the contrast media injection syringe 9d. 
The balloon catheter 5 has a dual lumen structure in which a guidewire passage lumen 5f extends through a contrast media passage lumen 5e. A balloon 5a is integrally formed at the distal end of the balloon catheter 5 which is introduced into the artery. The balloon catheter 5 has a balloon inflation port 5d at its proximal end. The guidewire passage lumen 5f extends from the distal end of the balloon catheter 5 to a guidewire passage opening 5b at a predetermined position of the balloon catheter 5 where the guidewire exits from the balloon catheter 5.
The balloon 5a of the balloon catheter 5 is connected to the contrast media passage port 5b through the contrast media passage lumen 5e. Thus, the contrast media may be injected into or extracted from the contrast media passage lumen 5e by manipulating a balloon inflation syringe 5c so as to inflate or deflate the balloon 5a. 
Moreover, the guidewire 6 is inserted into the guidewire passage lumen 5f. The guidewire passage lumen 5f formed inside the balloon catheter 5 extends from the distal end of the balloon catheter 5 to reach the guidewire passage opening 5b. It should be noted that the distal end of the guidewire passage lumen 5f is adjacent to the balloon 5a, and the proximal end of the guidewire passage lumen 5f forms the guidewire passage opening 5b. 
The guidewire 6 passes through the guidewire passage lumen 5f so that the distal portion of the guidewire 6 closely passes by the balloon 5a, and the proximal portion of the guidewire 6 passes through the guidewire passage opening 5b to exit from the balloon catheter 5.
As stated, the balloon catheter 5 of a dual lumen structure having the guidewire passage lumen 5f extending through the contrast media passage lumen 5e over almost the entire length of the balloon catheter 5 is called an “over-the-wire type balloon catheter”. On the contrary, a balloon catheter called a “monorail type balloon catheter” has an alternative structure in which a guidewire passage lumen is formed only in the vicinity of the distal portion of the balloon catheter and the guidewire exits from the middle of the balloon catheter.
Procedures of PCI treatment will be explained hereinafter with reference to the over-the-wire type balloon catheter. FIG. 1A is an illustration of conventional PCI treatment, and FIGS. 2A through 2D are sequential illustrations of PCI treatment.
(1) First, a portion of the femoral artery or the brachial artery of a patient is punctured with a needle to make an opening so that the introducer set 3 can be installed at the opening of the artery.
Then, the guiding catheter 4 is pushed through the introducer set 3 so as to reach a place near an inlet of the coronary artery (FIG. 1A).
(2) The Y-connector 2 is coupled with the guiding catheter 4. Subsequently, the guidewire 6 may be introduced into the Y-connector 2 so as to pass through the guiding catheter 4, thereby placing the distal end of the guidewire 6 in the coronary artery (FIGS. 1A and 1B).
(3) Next, the proximal end of the guidewire 6 is inserted into the guidewire passage lumen 5f adjacent to the balloon 5a of the balloon catheter 5. By thrusting the guidewire 6 forward, the proximal end of the guidewire 6 travels through the guidewire passage lumen 5f and exits from the guidewire passage opening 5b. The balloon catheter 5 is introduced into the artery by using the guidewire 6 as something like a railroad, so that the balloon catheter 5 can be easily slid through the artery.
(4) When the balloon 5a of the balloon catheter 5 arrives at the coronary artery, the contrast media is injected into the coronary artery by way of the manifold 9. With the help of the contrast media, the physician can identify the position of a stenotic lesion D (i.e. a narrow portion of the coronary artery) on an X-ray fluoroscope.
(5) By moving the balloon catheter backward or forward in the artery, the physician can place the balloon 5a mounted at the distal end of the balloon catheter 5 and the stent 8 mounted on the balloon 5a in the exact position of the stenotic lesion D (FIGS. 2A and 2B). When the contrast media contained in the balloon inflation syringe 5c is injected into the balloon 5a by way of the contrast media passage lumen 5e of the balloon catheter 5, the balloon 5a inflates so as to expand the stent 8 radially outward (FIG. 2C). The expanded stent holds up the artery walls that have been occluded due to the stenotic lesion D, so as to prevent recontraction of the walls. After the stent 8 is completely secured to the artery walls, the balloon 5a may be deflated by manipulating the balloon inflation syringe 5c conversely. Then, the balloon catheter 5 may be pulled out of the guiding catheter 4 to leave the stent 8 behind in the coronary artery (FIG. 2D).
The conventional PCI treatment stated above requires that the physician must move the balloon catheter 5 very minutely on the guidewire 6, relying on the sense of his or her hands while watching the X-ray fluoroscope, in order to place the balloon 5a in the exact position of the stenotic lesion D. However, it is very difficult for even a physician having great manual skills at pushing forward or pulling backward the balloon catheter in the artery, to adjust the balloon exactly to the position of the stenotic lesion in a short time. Thus, a key to the success of PCI treatment is that the stent should be installed exactly at the position of the stenotic lesion.
To position the balloon and stent exactly in the middle of the stenotic lesion of a coronary artery in PCI treatment, the physician has to inject the radioactive contrast dye multiple times into the coronary artery while moving the balloon catheter manually. The accurate positioning of the balloon and stent depends on the physician's hands and is not an easy task. The balloon and stent usually tend to move more or less than desired. However, even if the physician pays much attention to his or her manual movements, it is usually difficult to attain perfect positioning of the balloon and stent on a stenotic lesion of the coronary artery.
In PCI treatment using the conventional catheter apparatus, since the physician has to make small changes to the position of the balloon catheter by depending on his or her manual dexterity, it is very difficult to install the stent exactly at the position of the stenotic lesion (especially, at a curved or tortuous lesion) due to an excessive movement of the balloon and stent in the arteries. This may result in the installation of the stent in a less than optimal position, thereby causing less than ideal results. In addition, it takes much time to perform PCI treatment using the conventional catheter apparatus. Accordingly, the patient has to experience much pain due to the extended time of the operation, thereby adversely affecting the patient's prognosis.